1. FIELD OF THE INVENTION
The invention generally relates to movable or removable closures, especially to window assemblies. The invention also generally relates to static structures, especially composite fabricated panels. A further aspect of the invention generally relates to stock material, especially that having a structurally defined web or sheet.
2. DESCRIPTION OF THE PRIOR ART
Window units have been constructed from many different materials, often accommodating local climate or cost considerations. For example, many inexpensive windows are constructed with extruded metal frames, which offer simplicity of manufacture and dimensional stability, but often are not thermally efficient or pleasing to the eye. Wooden window frames may offer greater thermal efficiency and beauty, but they can be costly due to greater difficulty of manufacture, and maintenance is often a further problem.
U.S. Pat. No. 4,341,831 to Kleiss discloses an extrusion of multi-material construction. An aluminum or other sheet metal core is sheathed with polyurethane foam. The Kleiss disclosure explains that the prior art has suffered problems in bonding such a sheathing to a metal core, and hence, a new bonding material is proposed to cure the problem. Another patent showing a similar end structure is U.S. Pat. No. 4,130,976 to Kesseler et al., which uses an aluminum core with a bonded polyurethane sheathing.
U.S. Pat. No. 3,815,285 to Kuyper discloses a metal shielding that is designed to snap on to the exterior of wooden window sash as a weather protective device. The advantage gained is in coupling the low maintenance of the metal exterior with the beauty and insulating quality of the wood interior.
While the above noted patents are representative of efforts to improve window construction, they do not fully meet the desire of combined beauty, insulating value, dimensional stability, manufacturing ease, and low maintenance. Particularly in new construction, it is desirable to employ a window unit that is highly efficient in insulating value, both from the standpoint of materials of construction and tightness of construction. Thus, wood or other high insulating material is highly regarded as the material of construction. If the frame and sash can be produced in such a way to ensure that the window unit will maintain its dimensional integrity and structural shape, then the tightness of construction also will be satisfactory.
Additional desirable features of a window unit are that there be little or no maintenance, while, especially in residential applications, the window unit should offer beauty and warmth. Metal extrusions are satisfactory in terms of requiring little care, but metal does not hold an after-applied finish to a satisfactory degree. Wood is superior in terms of beauty and warmth, but maintenance is an on-going requirement. Plastic window constructions are intermediate wood and metal, in that they can hold an applied color or be extruded in a selected color. In addition, plastic offers good insulating value. However, plastic is known to degrade under ultraviolet light, which limits the life of such synthetic materials, especially in an exterior window construction. Further, plastics tend to be more flexible than metal or wood frame and sash and, thus, may lack the strength to hold a structural shape.
A purpose of the present invention is to provide a window unit having the unique combination of a high insulating value similar to that of wood; low maintenance similar to that achieved with metal; a complete surface finish having the pleasing warmth of wood but that requires no painting; and the strength and dimensional stability necessary to ensure continued performance at their original level for many years. In addition, such a window unit should be extremely simple in its method of manufacture so that its cost can be close to that of conventional wood and metal windows.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method of manufacture of this invention may comprise the following.